Integrated circuits (ICs) are typically assembled into packages by physically and electrically coupling them to a substrate. One or more IC packages can be physically and electrically coupled to a printed circuit board (PCB) to form an “electronic assembly”. An “electronic assembly” can be part of an “electronic system”. An “electronic system” is broadly defined herein as any product comprising an “electronic assembly”. Examples of electronic systems include computers (e.g., desktop, laptop, hand-held, server, etc.), wireless communications devices (e.g., cellular phones including Internet cellular phones, cordless phones, pagers, etc.), computer-related peripherals (e.g., printers, scanners, monitors, etc.), entertainment devices (e.g., televisions, radios, stereos, tape and compact disc players, video cassette recorders, digital video disk (DVD) equipment, MP3 (Motion Picture Experts Group, Audio Layer 3) players, etc.), and the like.
Integrated circuits (ICs) typically contain one or more functional circuit elements, such as data buffers, latching circuits, adder circuits, flip-flops, logic gates, driver circuits, decoder circuits, inverter circuits, counting circuits, registers, multiplexing circuits, amplifier circuits, sensing circuits, radio frequency circuits, and many other types of circuits. Power is supplied to the circuit elements of an IC through suitable power and ground connections, such as IC terminals or other types of connectors. Input signals are supplied to, and output signals are obtained from, the circuit elements of an IC through suitable input/output (I/O) connections, which can also be implemented in the form of IC terminals or other types of connectors.
In the field of electronic systems there is an incessant competitive pressure among manufacturers to drive the performance of their equipment up while driving down production costs. This is particularly true regarding the design, fabrication, and testing of ICs. ICs must generally be tested before they are incorporated into an electronic assembly in order to verify that each circuit element on the IC functions properly. During the life cycle of an IC, various factors, either singly or in combination, can contribute to faulty operation. For example, sub-optimal operation or even total failure can result from many factors, such as a change in the process used to fabricate the IC, shrinking the masks used to fabricate the IC to produce more chips per silicon wafer in order to reduce production costs, operation of the IC at a higher clock frequency in an attempt to improve performance, and so forth.
As a result of changes in production or operation, including the examples mentioned above, one or more circuit elements can display functional problems or failures when the IC is tested. Such problems or failures sometimes include sub-optimal performance issues referred to in the art as “escapes” or “speedpaths”. An “escape” refers to an imbalance in a resistive-capacitive (RC) characteristic of a circuit that results in sub-optimal performance, for example, when the circuit is operated within a particular frequency range. A “speedpath” refers to sub-optimal performance when timing issues occur over a critical path within a group of connected logic circuits. Escapes and speedpaths can often be resolved by adjusting the RC characteristic of the associated circuit(s).
In the prior art, when one or more circuit elements of an IC develops a functional problem, the only known solution is to redesign the relevant portion or portions of the IC or IC package, so that the problem is avoided. IC redesign generally necessitates the generation of a new set of masks at a very substantial cost, and it additionally incurs time delays that can jeopardize an IC producer's competitive position in the market.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a significant need in the art for IC circuit elements that can readily be corrected, without redesign, in the event their operation is tested to be sub-optimal, as well as for methods of designing, fabricating, and testing such ICs.